Time and time again entrepreneurs selling their businesses wonder why their customer base is not figured in the valuation equation. It is all about customer attrition rate (or the 1-Retention rate, if you will). Most of the cases there are no statistics available to proof, what the balance is of acquisition cost and the life time value of a customer is. So back to the good old industry multiples or a DCF that will be challenged by the acquirer on all these assumptions. Please read an article by Venture capitalist David Skok, explaining the relationships.